Engines may be automatically stopped and started to conserve fuel. However, each time the engine is automatically stopped and started, the possibility of increased engine emissions and driver dissatisfaction may increase. For example, if an engine rotates longer than is desired during engine stopping, the engine may pump air to the exhaust system such that operation of exhaust after treatment components may degrade. On the other hand, engine speed may increase during engine restarting such that more than a desired amount of engine torque is transferred to a vehicle's wheels during engine starting. Consequently, automatic engine stopping and starting may improve fuel economy at the expensed of engine emissions and driver satisfaction.
The inventors herein have recognized the above-mentioned limitations and have developed an engine system, comprising: an engine; a turbocharger coupled to the engine, the turbocharger including adjustable turbine vanes; and a controller including non-transient instructions to adjust a turbine vane position in response to a request to stop the engine, the position adjusted to increase engine exhaust backpressure.
By adjusting turbine vane position during engine stopping, it may be possible to reduce an amount of time for an engine to stop. Consequently, an amount of air pumped through the engine during engine stopping may be reduced. Further, the turbine vanes may be adjusted during engine starting to reduce engine speed overshoot. As a result, a desired amount of torque may be transferred from the engine to a vehicle's wheels during automatic engine starting.
The present description may provide several advantages. For example, the approach may reduce engine emissions during engine stopping. Additionally, the approach may improve engine starting. Further still, the approach may provide an improved driving experience for an automatically stopped and started vehicle.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.